Flexible mold, method of manufacturing same and method of manufacturing fine structures

ABSTRACT

A flexible mold ( 10 ) having a mold layer ( 11 ) that is provided on the surface thereof with a groove pattern ( 4 ) of specified shape and size, is constructed such that the mold layer contains a lithium salt of an organic fluorine compound as an antistatic agent.

FIELD OF THE INVENTION

The present invention relates to a mold and a method of manufacturing amold, and more particularly to a flexible mold and a method ofmanufacturing same which is useful for molding a fine structure andwhich is especially excellent in antistatic performance. The presentinvention also relates to a method of manufacturing a fine structureusing such a flexible mold. In particular, the present invention can beadvantageously used for manufacturing ribs of a back panel for a plasmadisplay panel.

BACKGROUND OF THE INVENTION

As is well known, with the advance and development of televisiontechnology, display devices using cathode ray tubes (CRTs) have beenproduced more and more economically mass-produced. In recent years,however, in place of these display devices using CRTs, thin andlight-weight flat display devices have attracted increasing attention.

One of the representative flat panel display devices is a liquid crystaldisplay (LCD) device, which has already been used widely as a compactdisplay device in a notebook-type personal computer, a mobile telephoneset, a personal digital assistant (PDA), and other portable electronicinformation apparatus. On the other hand, a plasma display panel is atypical display device as a thin and large screen size flat paneldisplay, and indeed begins to be used in business, and recently also inhome as a wall hanging television screen.

A PDP has the construction as shown schematically in FIG. 1. Although,in the illustrated example, the PDP 50 includes only one discharge cell56 for display for the sake of simplicity, it generally includes amultiplicity of minute discharge cells for display. More specifically,each discharge cell 56 for display is defined as surrounded by a pair ofglass substrates, that is, a front glass substrate 61 and a back glasssubstrate 51, which are spaced apart from and opposed to each other, anda fine structure of ribs 54 (barrier ribs, sometimes called partitionwalls or barriers) of a specified shape disposed between these glasssubstrates. The front glass substrate 61 comprises a transparent displayelectrode 63 consisting of scanning electrode and sustaining electrode,a transparent dielectric layer 62, and an overlying transparentprotective layer 64. The back glass substrate 51 comprises an addresselectrode 53 and an overlying dielectric layer 52. The displayelectrodes 63 and the address electrodes 53 are perpendicular to eachother, and are respectively arranged spaced apart in a regular pattern.Each discharge cell for display 56 has a fluorescent layer 55 formed onthe interior wall thereof, and has a rare gas (for example, Ne—Xe gas)hermetically sealed in the inside so as to enable light emitting displayby means of plasma discharge between above-mentioned electrodes.

In general, the ribs 54 consist of a fine structure of ceramics, andtogether with address electrodes 53, are usually provided on the backglass substrate 51, as shown schematically in FIG. 2, in advance offorming a back panel for PDP. Since the shape and dimensional precisionof the ribs significantly affect the performance of PDP, variousimprovement have been made on the mold used for manufacturing ribs andon the manufacturing method.

For example, a method has been proposed for manufacturing barrier ribscharacterized in that metal or glass is used as the mold material andthat coating liquid for forming ribs (partition wall) is disposedbetween the surface of a glass substrate and the mold material, and themold material is removed after the coating liquid is hardened andthereafter the substrate having the hardened coating liquid transferredthereon is baked (See Japanese Unexamined Patent Publication (Kokai) No.9-12336). The coating liquid has glass powder of low melting point as amain component.

Also, there has been proposed a method for manufacturing a substrate forPDP, comprising the steps of filling a mixture of ceramic or glasspowder with a solvent and a binder consisting of an organic additiveinto a silicone resin mold having cavities for the partition walls, andjoining this mixture integrally to a back panel formed of ceramics orglass (See Japanese Unexamined Patent Publication (Kokai) No. 9-134676).

Further, a method for manufacturing partition walls comprising the stepsof forming a partition wall member having a predetermined softness inthe shape of a plate of a predetermined thickness on a surface of asubstrate, molding the partition wall member under pressure by a pressmold provided with a shape corresponding to the partition wall to beformed, releasing the press mold from the partition wall member, andheat-treating the molded partition wall member at a predeterminedtemperature, has also been proposed (Japanese Unexamined PatentPublication (Kokai) No. 9-283017).

However, there is still a problem of electrification due to staticelectricity. Since a mold is usually formed of resin material,electrification due to static electricity is likely to occur during itsusage, and as a result, the mold tends to attract dust or powder of themolding material, or debris of ribs, so that frequent cleaning isrequired or the quality of obtained back panel may be adverselyaffected.

In order to address the problem of static electricity, one approach is amethod for antistatic processing of a mold used for manufacturing asubstrate for PDP, using an ionic conductive material, preferablylithium perchlorate. (See Japanese Unexamined Patent publication (Kokai)No. 2001-191345). Lithium perchlorate has relatively low ionizationenergy (high solubility in solvents) compared to other common salts, sothat, when blended to organic material such as resins, it increases theelectrical conductivity of the material. In accordance with this method,surface electrical resistance of the mold was decreased as a result ofthe antistatic processing, and adherence of dust or the like could bethereby avoided. In particular, when ionic conductivity was given to themold by this method, antistatic processing could be performedsuccessfully irrespective of surrounding environment

SUMMARY OF THE INVENTION

It was found, however, from a recent study that there remains a problemto be solved in this method of antistatic processing using lithiumperchlorate. Lithium perchlorate has high oxidative property, andtherefore, extreme care needs to be exercised not only in the handlingof the salt itself, but also in the handling of the mold material whenthe salt is blended to the material. Thus, mass production of themolding material or the mold containing lithium perchlorate is verydifficult.

In one aspect of the present invention, there is provided a flexiblemold comprising a mold layer having a groove pattern of specified shapeand size on the surface thereof, wherein said mold layer containslithium salt of an organic fluorine compound as an antistatic agent.

In another aspect of the present invention, there is provided a methodof manufacturing a flexible mold comprising a mold layer having a groovepattern of specified shape and size, said method comprising the stepsof:

forming a layer of a photocurable resin material by coating aphotocurable resin material containing a lithium salt of an organicfluorine compound as an antistatic agent to a predetermined filmthickness on a metal master pattern having on the surface thereof aprotrusion pattern in shape and size corresponding to said groovepattern of said mold;

laminating a transparent support consisting of a film of plasticmaterial on said metal master pattern to thereby form a laminate of saidmetal master pattern, said layer of a photocurable resin material, andsaid support;

irradiating said laminate with light from the side of the support toharden said layer of photocurable resin material; and

releasing said mold layer formed by the hardening of said photocurableresin material together with said support from said metal masterpattern.

In still another aspect of the present invention, there is provided amethod of manufacturing a fine structure having a protrusion pattern ofspecified shape and size on the surface of a substrate, said methodcomprising the steps of:

providing a flexible mold which has on the surface thereof a groovepattern of shape and size corresponding to said protrusion pattern, saidmold layer containing a lithium salt of an organic fluorine compound asan antistatic agent;

placing a curable molding material between said substrate and said moldlayer of said mold, and filling said molding material into said groovepattern of the mold;

curing said molding material and forming a fine structure consisting ofsaid substrate and the protrusion pattern integrally connected thereto;and

releasing said fine structure from the mold.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view schematically showing an example ofconventional PDP to which the present invention can be applied.

FIG. 2 is a perspective view showing a back panel for PDP used in thePDP of FIG. 1.

FIG. 3 is a perspective view showing a flexible mold according to anembodiment of the present invention.

FIG. 4 is a cross-sectional view taken along line IV-IV of the mold inFIG. 3.

FIG. 5 a-5 c is a cross-sectional view showing a method of manufacturinga flexible mold according to the present invention.

FIG. 6 a-6 c is a cross-sectional view showing a method of manufacturinga back panel for PDP according to the present invention.

FIG. 7 is a graph plotting the relation between surface resistance andadded amount of lithium salt solution relative to the amount of resinmaterial.

FIG. 8 is a graph plotting the relation between electrification voltageand added amount of lithium salt solution relative to the amount ofresin material.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The flexible mold and the method of manufacturing same, and the methodfor manufacturing a fine structure according to the present inventionmay be advantageously carried out in various embodiments, respectively.Embodiments of the present invention will be described in detail belowwith reference to manufacture of ribs for PDP as a typical example offine structures. It is to be understood that the present invention is byno means restricted to manufacture of ribs for PDP.

As has already been described with reference to FIG. 2, the ribs 54 forPDP are provided on the back glass substrate 51 to form a back panel forPDP. The spacing C of the ribs 54 (cell pitch) may vary depending uponthe size of the screen, and is typically in the range of about 150 to400 μm. In general, the ribs should satisfy two requirements, that is,“there should be no such defects as inclusion of air bubbles,deformation, and the like” and “the pitch of ribs should have highprecision.” With regard to the precision of the pitch, ribs are requiredto be provided at the specified location with little deviation relativeto address electrodes, and indeed the tolerance of the position iswithin a few tens of μm. If the positional error exceeds a few tens ofμm, light emitting condition for visible light is adversely affected,and satisfactory natural light emitting display cannot be expected.Since screen size has become increasingly large nowadays, the problem ofthe insufficient precision of the rib-pitch can be serious.

When ribs 54 are considered as a whole, the required dimensionalaccuracy of the total pitch R of ribs 54 (distance between the ribs 54at both ends; although only 5 ribs are shown in this Figure, usuallyabout 3000 ribs are present) is generally within a few tens ppm,although there may be some difference depending upon the size of thesubstrate or the shape of the ribs. In general, ribs can beadvantageously formed using a flexible mold comprising a support and amold layer with a groove-pattern supported by the support, and the totalpitch of the mold (distance between groove portions at both ends) isalso required to satisfy the same dimensional accuracy of a few tens ppmor less as the ribs. In accordance with the present invention,satisfactory dimensional accuracy can be obtained for the pitch of ribsas well as for total pitch.

First, the flexible mold of the present invention useful formanufacturing a back panel for PDP as shown in FIG. 2 will be describedwith regard to the construction and the method of manufacturing same.

FIG. 3 is a partial perspective view showing schematically a flexiblemold according to a preferred embodiment of the present invention. Ascan be seen from FIG. 3, the flexible mold 10 is designed for themanufacture of a back panel for PDP having a straight rib pattern with aplurality of ribs 54 arranged in parallel to each other as shown in FIG.2. The flexible mold 10 may be modified in design, although not shown,such that it permits the manufacture of a glass substrate for a PDP backpanel having a lattice-shaped rib pattern in which a plurality of ribsare arranged generally in parallel so as to cross each other at aconstant spacing, or other type of back panel for PDP.

FIG. 4 is a cross-sectional view taken along the line IV-IV of FIG. 3,although the shape and size of the flexible mold of FIG. 3 is notaccurately reproduced. As shown in FIG. 4, the flexible mold 10 has agroove pattern of predetermined shape and size on the surface thereof.The groove pattern is a straight rib pattern composed of a plurality ofgrooves 4 arranged generally in parallel to each other at a constantspacing. The grooves 4 have sides (side walls) preferably inclined asshown in the FIG. 4 so as to permit the ribs to be easily released fromthe mold. Also, terminating ends of the grooves extending in thelongitudinal direction have preferably inclined end surfaces. The shapeand size of the grooves 4 may be varied, respectively, in wide range inaccordance with the shape and size of the ribs for PDP that aremanufactured using the mold. For example, in the case of the mold 10shown in FIG. 4, as measured on the surface of the mold layer 11, depthd of each groove 4 is typically in the range of about 100 to 400 μm, andpreferably in the range of about 150 to 300 μm. Width w of each groove 4is typically in the range of about 5 to 250 μm, and preferably in therange of about 100 to 200 μm. The length of each groove varies widelydepending upon the groove pattern, and cannot be generally defined.Width 1 of the plane portion that lies between two grooves 4 istypically in the range of about 50 to 250 μm, and preferably in therange of about 100 to 200 μm.

As can be easily understood, the flexible mold 10 is formed so as to beprovided on the surface with grooves 4 opened on top plane as shown inFIG. 4, so that it can be advantageously used for molding ribs for PDPhaving a protrusion pattern, for example, a straight protrusion pattern,a lattice-like protrusion pattern, etc. The flexible mold 10 may beformed only of a mold layer 11, or may include additional layers asrequired, or optional processing may be performed on various layerscomposing the mold. The flexible mold is preferably composed of asupport 1 and a mold layer 11 having a groove 4 thereon. Each of thesupport 1 and the mold layer 11 is preferably transparent.

The flexible mold of the present invention is characterized in that themold layer contains lithium salt of an organic fluorine compound as anantistatic agent. The lithium salt of an organic fluorine compound isused, when blended to the constituent material (molding material,preferably resin material) of the mold layer, in an amount effective forsufficient function as an antistatic agent in the blend or obtained moldand for avoiding occurrence of undesired electrification due to staticelectricity.

The lithium salt of an organic fluorine compound to be blended to themold layer used in the present invention is not particularly restricted.Lithium salt of an organic fluorine compound suitable in the practice ofthe present invention is preferably:

(1) a compound having excellent stability to moisture, that is, acompound that does not substantially decomposed in the presence ofmoisture;

(2) a compound having excellent thermal stability, that is a compoundthat does not substantially decomposed when heated to an elevatedtemperature, for example, to about 100° C.; more specifically, acompound that remains stable and does not give rise to thermaldecomposition when heated to an elevated temperature of 200° C. orhigher, preferably about 300 to 350° C., during the course of moldingprocess using the mold;

(3) a compound having excellent electrical conductivity, that is, acomponent that exhibits, for example, electrical conductivity of about 5to 15 mS/cm, preferably about 10 to 12 mS/cm, when measured in PC/DME(propylene carbonate/dimethoxyethane) at the concentration of 1 M(mole).

The lithium salt compound used in the present invention is required tosatisfy at least one of these requirements, and satisfies mostpreferably all of these requirements.

The present inventor has found that suitable lithium salts of organicfluorine compounds to be used in the invention include, but are notlimited to, CF₃SO₃Li, (C_(n)F_(2n+1)SO₂)₂NLi wherein n is an integer of1 or 2, LiSO₃C₂F₄SO₃Li, CF₃CO₂Li, C₄F₉SO₃Li, (CF₃CO)₂NLi, (CF₃SO₂)₃CLi,and (CF₃SO₂)₂CFLi. These lithium salts may be used alone or in a mixtureof two or more of them.

These lithium salts can be used advantageously in the present inventionfor reasons as described below. Lithium salts such as CF₃SO₃Li,(CF₃SO₂)₂NLi, (C₂F₅SO₂)₂NLi are preferred. Also, it has been confirmedby the applicants that lithium salts such as CF₃SO₃Li, (CF₃SO₂)₂NLi,(C₂F₅SO₂)₂NLi are stable at temperature up to 350° C. In addition, theselithium salts have a low oxidative property so that they can be easilyblended to the mold material and there is no difficulty in themanagement of the obtained blend. Thus, the entire process beginningfrom the preparation of the mold material, manufacture of the mold, tothe storage of the mold, can be implemented far more easily.

Above-mentioned lithium salts of organic fluorine compounds haveremarkably excellent antistatic performance. These lithium salts havelow ionization energy like lithium perchlorate, and can beadvantageously used as an antistatic agent. In general, among a seriesof lithium salts of organic fluorine compounds, lithium salts having—SO₂ group in the molecule, for example (C_(n)F_(2n+1)SO₂)₂NLi, haveespecially high electrical conductivity. In particular, imide salts suchas (C_(n)F_(2n+1)SO₂)₂NLi have two —SO₂ groups in the molecule andespecially high electrical conductivity can be expected from thesesalts.

Above-described lithium salts of organic fluorine compounds may beblended to the mold material as they are, or may be preferably dissolvedin a lithium salt-ionizing solvent and then blended to the moldmaterial. Suitable ionizing solvents are polar solvents having a highboiling point of about 200° C. or higher. Examples of polar solventshaving a high boiling point suitable for implementing the presentinvention include, but are not limited to, ethylene carbonate, propylenecarbonate, ethylene glycol, lactone, and their derivatives. Theseionizing solvents may be used alone or in combination of two or more ofthem. These ionizing solvent may be used in varied amount for dissolvinglithium salts, and is typically used preferably in an amount in therange of about 0.01 to 10% by weight, more preferably in the range ofabout 0.1 to 1.0% by weight, relative to total weight of the moldmaterial.

Effective blended amount of lithium salt in the mold layer may be varieddepending upon various factors such as the kind of lithium salt and thekind of the mold material, and typically, it is preferably in the rangeof about 0.01 to 5% by weight, and more preferably in the range of about0.05 to 1% by weight, relative to total weight of the mold material. Ifthe blended amount of such lithium salt is less than 0.01% by weight,desired antistatic effect cannot be obtained. If, on the contrary, theblended amount is more than 5% by weight, the antistatic effect issaturated.

The mold layer is preferably formed of hardened piece of a photocurableresin material. The mold layer that can be used advantageously forimplementing the present invention is a thin film that is formed byhardening a resin material by application of heat, light, or otherenergy after the film is formed by coating a curable resin material. Thecurable resin material is, therefore, preferably a heat-curable resinmaterial or photocurable resin material. Especially, a photocurableresin material can be advantageously used, since it does not require alarge and long heating furnace for forming the mold layer, and hardeningcan be carried out in relatively shore period. The photocurable resinmaterial is preferably a photocurable monomer or oligomer, morepreferably an acrylic monomer or oligomer, and most preferably a(meth)acrylate, that is, an acrylate or methacrylate, monomer oroligomer.

More specifically, acrylic monomers suitable for forming the mold layerinclude, but are not limited to, urethane acrylate, polyester acrylate,polyether acrylate, acryl amide, acryl nitrile, acrylic acid, acrylicester. Acrylic oligomers suitable for forming the mold layer include,but are not limited to, urethane acrylate oligomer, epoxy acrylateoligomer. In particular, urethane acrylate and its oligomer can providea flexible and strong hardened piece after curing, and has a very highcuring speed among acrylates in general, so that it can contribute toimprovement of the productivity of the mold. In addition, when theseacrylate monomers or oligomers are used, the obtained mold layer becomesoptically transparent. Thus, the flexible mold having such a mold layerpermits a photocurable molding material to be used in the manufacture ofPDP ribs or other fine structures. These acrylic monomers or oligomersmay be used alone or in an arbitrary combination of two or more of them.Although features of acrylate monomers or oligomers are described above,similar features can be obtained for methacrylate monomers or oligomers.

The curable resin material may contain an optional additives. Forexample, when the curable resin material is a photocurable resinmaterial, suitable additives may include a photoinitiator. For example,as a photoinitiator, the most suitable compound should be selected inaccordance with the type of the curable resin material, and examples mayinclude 2-hydroxy-2-methyl-1-phenyl-propane-1-on,bis(2,4,6-trimethylbenzoyl)-phenyl phosphin oxide. These photoinitiatorsmay be used alone or in combination of two or more of them. Thephotoinitiator may be used in widely variable amount depending upon thetype of the curable resin material, and is typically used in an amountin the range of about 0.1 to 10% by weight, and preferably in the rangeof about 0.5 to 2% by weight, relative to the total amount of thecurable resin material.

In addition to the lithium salt of an organic fluorine compound used inthe present invention, other antistatic agent such as lithiumperchlorate, lithium nitrate, etc., may be used in additional smallamount, as long as the operative effect of the present invention is notadversely affected, or rather, the operative effect of the presentinvention can be thereby improved.

Other additives that can be used include, for example, aminesurfactants, ionic surfactants, etc.

The mold layer may be used in varied thickness depending upon suchfactors as shape and size of ribs. Typically, the thickness of the moldlayer is in the range of about 5 to 1000 μm, preferably in the range ofabout 100 to 500 μm. If the mold layer is too thin, ribs of specifiedheight cannot be formed. The thickness of the mold layer may be suitablymodified depending upon the presence or absence of a support.

The mold layer is preferably carried by a support. The support thatcarries the mold layer may be composed of an arbitrary material, andsince flexibility suitable for handling needs to be given to the mold,it is preferably composed of a support material having suitable hardnessor softness.

With regard to hardness of the support material, it is preferable toselect, as the support material, a material that is much harder than themold material forming the mold layer involved in forming the groove(preferably, a photocurable material such as photocurable resins),preferably a plastic material having a high glass transitiontemperature. Since, in general, hardening shrinkage of a photocurableresins is about a few %, if a soft plastic film is used for the support,the hardening shrinkage of the former may give rise to dimensionalchange in the support itself and dimensional accuracy of the groovepitch cannot be controlled within a few tens of ppm. If, on thecontrary, the plastic film is hard, dimensional accuracy of the supportitself can be maintained even after the hardening shrinkage of thephotocurable resin, and the dimensional accuracy of the groove pitch canbe maintained in high precision. Also, when the plastic film is hard,the pitch variation during formation of the ribs can be kept small. Thisis advantageous both in moldability and in dimensional accuracy.Examples of hard plastic film suitable for implementing the presentinvention include those listed below.

If the plastic film is hard, since dimensional accuracy of the groovepitch of the mold depends only upon the dimensional change of theplastic film, in order to provide a mold having desired dimensionalaccuracy of the groove pitch, it is sufficient to performpost-processing such that dimension of the plastic film is as intendedand shows no change in the mold after the manufacture.

Hardness of the support material may be expressed, for example, asrigidity to tension, that is, as tensile strength. The tensile strengthof the support material is typically at least about 5 kg/mm², andpreferably at least about 10 kg/mm². If the tensile strength of thesupport material is less than 5 kg/mm², workability in the handling isdegraded when the obtained mold is released from the metal masterpattern 5 or when the PDP rib is released from the mold, and this maylead to breaking or rupture.

Preferable support for implementing the present invention is a film ofplastic material having good workability in handling as well as goodhardness. Examples of plastic material suitable for the support include,but are not limited to, polyethylene terephthalate (PET), polyethylenenaphthalate (PEN), stretched polypropylene, polycarbonate, triacetate,etc. Among them, PET film is particularly useful for the support, andfor example, polyester film such as Tetron™ film may be advantageouslyused as the support. These plastic films may be used alone as a singlelayer film or two or more of them may be used in combination as acomposite film or a laminated film.

Above-described plastic film or other support may be used in variedthickness depending upon the construction of the mold or the PDP, andthe thickness is typically in the range of about 50 to 500 μm, andpreferably in the range of about 100 to 300 μm. If thickness of thesupport is outside of above-mentioned range, workability in handling maybe degraded. The thicker the support, the more advantageous it is instrength.

The present invention also relates to a method of manufacturing theflexible mold as described above. The method of manufacturing theflexible mold according to the present invention comprises, inparticular, the steps of:

forming a layer of a photocurable resin material by coating aphotocurable resin material containing a lithium salt of an organicfluorine compound as an antistatic agent to a predetermined filmthickness on a metal master pattern having on the surface thereof aprotrusion pattern in shape and size corresponding to the groove patternof the mold;

laminating a transparent support consisting of a film of plasticmaterial on said metal master pattern to thereby form a laminate of saidmetal master pattern, said layer of a photocurable resin material, andsaid support;

irradiating said laminate with light from the side of the support toharden said layer of photocurable resin material; and

releasing said mold layer formed by the hardening of said photocurableresin material together with said support from said metal masterpattern.

The method of manufacturing the flexible mold according to the presentinvention may be implemented in various modifications within the scopeof the present invention. For example, a flexible mold for manufacturinga substrate (back panel) for PDP as shown in FIG. 2, which has theconstruction as shown schematically in FIGS. 3 and 4, may bemanufactured advantageously by following steps as shown in order in FIG.5.

First, as shown in FIG. 5(A), a metal master pattern 5 having shape andsize corresponding to the substrate for PDP to be manufactured, asupport 1 consisting of a transparent plastic film (hereinafter referredto as support film), and a laminate roll 23 are provided. The metalmaster pattern 5 has partition walls 14 on the surface thereof which areof the same pattern and shape as the ribs on the back panel for PDP.Thus, a space (recess) 15 defined by adjoining partition walls 14 is tobe used as a discharge display cell in PDP. Taper may be provided in theupper end portion of the partition wall 14 so as to prevent inclusion ofbubbles. Inclined surface may be provided at the terminating end portionof respective partition walls to facilitate removal of the obtained moldfrom the metal master pattern. In any event, by providing a metal masterpattern having identical shape to the final form of ribs, need ofprocessing of end portion of ribs after the manufacture can beeliminated, and occurrence of defects due to debris produced in theprocessing of end portion can be avoided. In the present manufacturingmethod, all the material for forming ribs is hardened so that verylittle residue of molding material is left on the metal master pattern,and therefore, reuse of the metal master pattern becomes quite easy. Thelaminate roll 23 consists of a rubber roll and serves to press thesupport film 1 to the metal master pattern 5. Other known or customarylaminating means may be used in place of the laminate roll. The supportfilm 1 consists of a polyester film or other transparent plastic film asdescribed above.

Then, using known or customary coating means such as a knife coater or abar coater (not shown), photocurable mold material 11 is coated to theend surface of the metal master pattern 5 in a specified amount. When aflexible and elastic material is used as the support film 1, even ifshrinkage of the photocurable mold material 11 takes place, closecontact with the support film 1 prevents dimensional change of 10 ppm orgreater as long as the support film itself does not deform.

Prior to laminating process, aging treatment is preferably performedunder the manufacturing environment in order to avoid dimensional changeof the support film due to humidity. Unless the aging treatment isperformed, unacceptable dimensional variation (for example, variation onthe order of 300 ppm) may arise in the obtained mold.

Next, the laminate roll is slid on the metal master pattern 5 in thedirection of an arrow. As a result of this laminating process, the moldmaterial 11 is evenly distributed evenly in specified thickness, andgaps between the partition walls 14 are filled with the mold material11.

After the laminating process has been completed, with the support film 1laminated on the metal master pattern 5 as shown in FIG. 5(B), the moldmaterial is irradiated with light (hv) as shown by arrows. If thesupport film 1 does not include light scattering elements such as airbubbles, and is formed uniformly of the transparent material, theirradiated light can reach the mold material evenly with littleattenuation. As a result of irradiation, the mold material is hardenedefficiently and forms a homogeneous mold layer 11 having the supportfilm 1 adhered thereto. Thus, a flexible mold is obtained with thesupport film 1 and the mold layer 11 integrally joined in one unit.Since ultraviolet light of wavelength in the range of 350 to 450 nm, forexample, can be used, this process is advantageous in that it is notnecessary to use a light source generating large amount of heat, forexample, a high pressure mercury lamp such as a fusion lamp. Sincethermal deformation of the support film or the mold layer during thephotocuring can be thus avoided, leading to another advantage that thepitch can be controlled in high precision.

Next, as shown in FIG. 5(C), the flexible mold 10 is released withoutimpairing its integrity from the metal master pattern 5. If necessary,the flexible mold 10 may be placed in a thermohygrostat and subjected toa conditioning process following a predetermined schedule. With thisconditioning process, undesired dimensional change of the obtained moldcan be suppressed, and a mold having proper size can be obtained.

The flexible mold of the present invention can be manufacturedrelatively simply, irrespective of the size and dimensions, as long assuitable well known and conventional laminating means and coating meansare employed. Thus, in accordance with the present invention, incontrast to the conventional manufacturing process using vacuumequipment such as vacuum press molding machine etc., a large-sizeflexible mold can be manufactured simply and easily with no limitation.

Moreover, the flexible mold of the present invention is useful in themanufacture of various fine structures. For example, the flexible moldof the invention is useful for molding of ribs for PDP with straight ribpattern or lattice rib pattern. Thus, by using the flexible mold, alarge screen size PDP with rib structure that does not permit leakage ofUV light from discharge cells for display can be easily manufacturedsimply by employing a laminate roll in place of vacuum equipment and/orcomplicated process.

The present invention is therefore also directed to a manufacturingprocess for manufacturing fine structures using the flexible mold of theinvention. The method of manufacturing a fine structure according to thepresent invention comprises, in particular, the steps of:

providing a flexible mold that has on the surface thereof a groovepattern of shape and size corresponding to the protrusion pattern of thefine structure, said mold layer containing a lithium salt of an organicfluorine compound as an antistatic agent;

placing a curable molding material between said substrate and said moldlayer of said mold, and filling said molding material into said groovepattern of the mold;

curing said molding material and forming a fine structure consisting ofsaid substrate and the protrusion pattern integrally connected thereto;and

releasing said fine structure from said mold.

As can be understood from the foregoing, the fine structure may havevarious structures, and is typically exemplified by a substrate (backpanel) for PDPs which is provided with ribs on a glass plate. Themanufacturing process of a substrate for PDP as shown in FIG. 2 will bedescribed below with reference to FIG. 6. Manufacturing equipment asshown in FIGS. 1 to 3 of Japanese Unexamined Patent Publication (Kokai)No. 2001-191345, for example, can be advantageously used in implementingthis manufacturing process.

First, a glass plate is provided with electrodes arranged in parallel toeach other at a constant spacing, and is set on a surface plate. Then,as shown in FIG. 6(A), the flexible mold 10 of the present invention isplaced at specified position on the glass plate 31, and the glass plate31 and the mold 10 are suitably aligned with each other. The flexiblemold 10 is preferably provided in advance with an alignment mark such asa cross mark formed in an area other than the rib-forming area. Sincethe mold 10 is optically transparent, the alignment with the electrodeson the glass plate 31 can be carried out easily. More specifically, thealignment may be performed visually, or by using a sensor such as a CCDcamera, such that the grooves of the mold 10 are set in parallel to theelectrodes on the glass plate 31. If necessary, temperature and humiditymay be adjusted to bring the grooves into coincidence with the spacingbetween adjoining electrodes on the glass plate 31. This adjustment isrequired because the mold 10 and the glass plate 31 expands or contractsto different extent in accordance with change of temperature andhumidity. Therefore, after the alignment of the glass plate 31 with themold 10 has been completed, temperature and humidity need to becontrolled so as to remain constant. This control method is especiallyeffective in the manufacture of a large area substrate for PDP.

Then, a laminate roll 23 is placed on an end portion of the mold 10. Thelaminate roll 23 is preferably a rubber roll. Here, the one end portionof the mold 10 is preferably fixed on the glass plate 31, so thatdisplacement of the mold 10 with respect to the glass plate 31 may beavoided after the alignment has been completed.

Next, the other free end portion of the mold 10 is raised by a holder(not shown) above the laminate roll 23 to expose the glass plate 31. Atthis time, the mold 10 should not be subjected to tension. This is forpreventing the mold 10 from being wrinkled and for maintaining thealignment of the mold 10 with the glass plate 31. Other means may beemployed as long as the alignment can be maintained. In the presentmanufacturing process, since the mold 10 has elasticity, the mold 10 canbe restored at the time of laminating process, accurately to the initialposition of the alignment after it has been raised as shown in theFigure.

Then, specified amount of rib precursor 33 required to form ribs issupplied onto the glass plate 31. The rib precursor can be suppliedusing, for example, a hopper with nozzle for paste.

As used herein, the term “rib precursor” means any molding material thatcan be formed into the rib molding as the intended end product, andthere is no special limitation as long as the rib molding can be formed.The rib precursor may be thermo-setting or photocurable. In particular,a photocurable rib precursor can be used very effectively in combinationwith the above-described transparent flexible mold. As described above,the flexible mold rarely includes air bubbles or defects such asdeformations, and can suppress uneven scattering of light. Therefore,the molding material is hardened uniformly to form ribs of constant andgood quality.

An example of composition suitable for the rib precursor is acomposition basically including:

(1) a ceramic component for giving the shape of the ribs, such asaluminum oxide;

(2) a glass component for filling the gap between the ceramic componentand adding density to the ribs, such as lead glass or phosphate glass;and

(3) a binder for containing, holding and binding ceramic component witheach other, and its curing agent or polymerization initiator. Hardeningof the binder component is preferably achieved not by heating orwarming, but by irradiation with light, since thermal deformation of theglass plate no longer needs to be considered in this case. If necessary,in order to lower the temperature for removing the binder component, anoxidation catalyst consisting of oxides, salts or complexes of chromium(Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu),zinc (Zn), indium (In) or tin (Sn), ruthenium (Ru), rhodium (Rh),palladium (Pd), silver (Ag), iridium (Ir), platinum (Pt), gold (Au) orcerium (Ce) may be added to the composition.

In the practice of the illustrated manufacturing process, the ribprecursor 33 is not supplied uniformly to the entire glass plate 31. Asshown in FIG. 6(A), the rib precursor 33 has only to be supplied to theportion of the glass plate 31 near the laminate roll 23, since, in thestep described later, the laminate roll 23 is moved on the mold 10 so asto spread the rib precursor 33 uniformly on the entire glass plate 31.In this case, it is desirable that the rib precursor 33 has viscosity oftypically about 20,000 cps or less, preferably about 5,000 cps or less.If the viscosity of the rib precursor is higher than about 20,000 cps,it is difficult to spread the rib precursor sufficiently with thelaminate roll, and as a result, air may be entrained into the grooveportion of the mold, and may become a cause of defects of the ribs. Infact, if the viscosity of the rib precursor is about 20,000 cps or less,the laminate roll needs to be moved from one end of the glass plate tothe other end only once for spreading the rib precursor uniformlybetween the glass plate and the mold and filling all groove portionsuniformly without giving rise to inclusion of air bubbles. Method ofsupplying the rib precursor is not restricted to the above-describedmethod. For example, the rib precursor may be coated to the entiresurface of the glass plate, although this is not shown. In this case,the rib precursor for coating has the same viscosity as described above.In particular, when ribs in the shape of a lattice pattern are to beformed, the viscosity of the rib precursor is typically about 20,000 cpsor less, preferably 5,000 cps or less.

Next, a rotary motor (not shown) is driven to move the laminate roll 23on the mold 10 as shown by the arrow in FIG. 6(A). While the laminateroll 23 is thus moved on the mold 10, pressure is applied to the mold 10successively from one end portion to the other end portion by the weightof the laminate roll 23 itself so that the rib precursor 33 is spreadbetween the glass plate 31 and the mold 10 and is filled into thegrooves of the mold 10. Thus, the rib precursor successively replacesair in the grooves and is filled into it. The rib precursor may bespread in the thickness in the range of a few μm to a few tens μm bysuitably controlling the viscosity of the rib precursor, or thediameter, weight or moving speed of the laminate roll.

With the illustrated manufacturing process, the grooves of the mold alsoacts channels for air so that, even if air is captured in the groove,the air can be efficiently discharged through this channel out of themold to surroundings when pressure is applied as described above.Consequently, the present manufacturing process can prevent inclusion ofremaining air bubbles even if the grooves are filled with rib precursorunder atmospheric pressure. In other words, reduced pressure needs notbe applied in filling the rib precursor. It is to be understood thatreduced pressure may be utilized to further facilitate removal of airbubbles.

Then, the rib precursor is hardened. If the rib precursor 33 which arespread on the glass plate 31 is photocurable, the laminate consisting ofthe glass plate 31 and the mold 10 is placed in a irradiation apparatus(not shown), and the rib precursor 33 is irradiated with light such asultraviolet ray (UV) via the glass plate 31 and the mold 10, as shown inFIG. 6(B). After hardening, a molding of the rib precursor, that is, therib per se is obtained.

Finally, with the obtained rib 34 adhered to the glass plate 31, theglass plate 31 and the mold 10 are removed from the irradiationapparatus, and the mold 10 is separated and removed, as shown in FIG.6(C). Since the mold 10 of the present invention is excellent in ease ofhandling, if a material of low adhesion is used as coating layer of themold, the mold 10 can be easily separated and removed with small forcewithout damaging the rib 34 adhered to the glass plate 31. It should beappreciated that no large scale apparatus is required for the separationand removal of the mold.

The present invention will now be described more specifically withreference to the following examples. It should be easily understood bythose skilled in the art that the present invention is by no meansrestricted to these examples.

EXAMPLES Example 1

Fabrication of the Flexible Mold:

For the manufacture of back panel for PDP, a rectangular metal masterpattern having ribs (partition walls) in a straight pattern wasprepared. More specifically, the metal master pattern had ribs with thecross section along the longitudinal direction in the shape of isoscelestrapezoid arranged at a constant pitch. The space (recess) defined byadjoining ribs corresponds to a discharge cell for display for PDP. Eachof the ribs was 135 μm in height, 60 μm in top width, and 120 μm inbottom width. Pitch (distance between the centers of adjoining ribs) was300 μm, and number of ribs was 3000. Total pitch (distance between thecenters of ribs at both ends) was 900.221 mm.

In order to be used in forming the mold layer of the mold, aphotocurable resin was prepared by mixing aliphatic urethane acrylateoligomer (manufactured by Daicel-UCB, Co.), phenoxyethyl acrylate, and2-hydroxy-2-methyl-1-phenyl-propane-1-one (photoinitiator: Trade name“Darocure 1173”; manufactured by Chiba Speciality chemicals, Co.) inweight ratio of 100:25:1.25. Then, a propylene carbonate solution of(CF₃SO₂)₂NLi was added to this mixture as an antistatic agent. Theamount of the added antistatic agent was 0.5% by weight relative to theamount of UV-curable resin. Concentration of the lithium salt was 20% byweight. The UV-curable resin for forming mold layer was thus obtained.

In order to be used as the support for the mold, PET film of 1300 mm inwidth and 100 μm in thickness (Trade name, “HPE”; manufactured by TeijinCo.) was provided.

Then, the above-described UV-curable resin was coated in the shape of aline to the upstream end of the prepared metal master pattern. Then,above-described PET film was laminated on the surface of the metalmaster pattern so as to cover it. When a laminate roll was usedcarefully to press the PET film, the UV-curable resin was filled intothe recesses of the metal master pattern.

In this state, the UV-curable resin was irradiated via the PET filmusing a fluorescent lamp (manufactured by Mitsubishi-Osram Co.) withlight having wavelength of 300 to 400 nm for 30 seconds. The UV-curableresin was hardened and the mold layer was thus obtained. Then the PETfilm together with the mold layer was released from the metal masterpattern, and thus a flexible mold having a multiplicity of grooves ofshape and size corresponding to the ribs on the metal master pattern wasobtained. Thickness of the mold layer was about 300 μm.

Fabrication of a Back Panel for PDP:

After the flexible mold was fabricated as described above, the mold wasarranged in alignment to a glass substrate for PDP. The mold was placedwith the groove-pattern facing the glass substrate. Then, photosensitiveceramic paste was filled between the mold and the glass substrate. Theceramic paste used had following composition.

Photocurable Oligomer:

dimethacrylate of bisphenol-A-diglycidyl ether (manufactured by KyoeisyaChemical Co.) 21.0 g

Photocurable Monomer:

triethyleneglycol dimethacrylate (manufactured by Wako Pure ChemicalsIndustries, Co.). 9.0 g

Diluent:

1,3-butanediol (manufactured by Wako Pure Chemical Industries, Co.) 30.0g

Photoinitiator:

bis(2,4,6-trimethylbenzoyl)-phenyl phosphine oxide (Trade name “Irgacure819”; manufactured by Chiba Speciality Chemicals, Co.)

0.3 g

Surfactant:

phosphate propoxyalkyl polyol 3.0 g

Inorganic Particle:

mixed powder of lead glass frit and ceramic particles (manufactured byAsahi Glass, Co.) −180.0 g

After the ceramic paste has been filled, the mold was laminated so as tocover the surface of the glass substrate. When laminate roll was usedcarefully to press the mold against the substrate, the ceramic paste wascompletely filled into the grooves of the mold.

In this state, a fluorescent lamp (manufactured by Philips Co.) was usedto irradiate the ceramic paste with light having wavelength of 400 to450 nm for 30 seconds from both sides via the mold and the glasssubstrate. The ceramic paste was hardened to form the ribs. Then, theglass substrate together with the ribs formed thereon was separated fromthe mold, and a back panel for PDP consisting of the glass substratewith ribs formed thereon was obtained as intended.

Example 2

The procedure described in Example 1 was repeated to fabricate aflexible mold. In the present Example, in order to evaluate the effectof concentration of lithium salt solution and added amount of thesolution relative to the amount of resin upon surface resistance of themold, lithium salt solutions of different concentration, as shown inFIG. 7, that is:

C1 . . . 1% by weight propylene carbonate solution

C2 . . . 2% by weight propylene carbonate solution

C5 . . . 5% by weight propylene carbonate solution

C10 . . . 10% by weight propylene carbonate solution

C20 . . . 20% by weight propylene carbonate solution

were used, and blended amount of the lithium salt solution relative tothe amount of resin was also varied in the range of 1 to 5% by weight.

After each of the lithium salt solutions was blended to resin indifferent blending amount to prepare UV-curable resin, each of theUV-curable resins was coated to PET film of 100 μm in thickness andirradiated with UV-light to fabricate the mold with a mold layer of 300μm in thickness.

With obtained molds, surface resistance (Ω/cm²) of the mold layer wasmeasured at the temperature of 22° C. and relative humidity (RH) of 55%,and measurement result as plotted in FIG. 7 was obtained. Formeasurement of surface resistance, a commercially available measurementapparatus (Model 1272A; manufactured by Monroe Electronics Inc.) wasused. As can be seen from the graph shown in FIG. 7, surface resistanceof the mold can be lowered by increasing the concentration of addedlithium salt solution and blended amount of the solution relative to thetotal amount of resin. In general, when blended amount of lithium saltsolution relative to resin is in the range of about 0.01 to 5% byweight, satisfactorily lowered surface resistance can be obtained.

Example 3

The procedure described in Example 1 above was repeated to fabricate aflexible mold. In the present Example, in order to evaluate the effectof blended amount of lithium salt solution relative to total amount ofresin upon electrification voltage of the mold, lithium salt solution inthe form of 20% by weight propylene carbonate solution (C20) was usedand the blended amount of the lithium salt solution relative to totalamount of resin was varied in the range of 0.0 to 2.0% by weight.

After UV-curable resin was prepared by blending the lithium saltsolution in different blended amount, each UV-curable resin was coatedto a PET film of 100 μm in thickness and was irradiated with UV light toform the mold with a mold layer of 300 μm in thickness.

Next, each mold was cut to form a test specimen of length 850 mm×width350 mm. On this test specimen of mold layer, a PET film (Trade name“HPE”: manufactured by Teijin Co.) of same size as the test specimen and100 μm in thickness was adhered. The test specimen was fixed at one sidethereof to a transverse member and was suspended vertically like aNoren. With the test specimen suspended, the adhered PET film was peeledoff at the speed of about 300 mm/s, and the electrification voltage (Kv)immediately after peeling was measured at temperature of 22° C. andrelative humidity (RH) of 55%. Measurement result as plotted in FIG. 8was thus obtained. For the measurement of electrification voltage, acommercially available electrification measuring apparatus (ModelFMX-002; manufactured by SIMCO Co.) was used. As can be seen from thegraph shown in FIG. 8, the electrification voltage of the mold can belowered by adding the lithium salt solution, and by increasing theblended amount of the lithium salt solution relative to the total amountof resin.

1. A flexible mold comprising a mold layer having on the surface thereofa groove-pattern of specified shape and size, wherein said mold layercomprises a lithium salt of an organic fluorine compound as anantistatic agent.
 2. A flexible mold according to claim 1, wherein saidlithium salt of an organic fluorine compound is at least one lithiumsalt selected from the group consisting of CF₃SO₃Li,(C_(n)F_(2n+1)SO₂)₂NLi wherein n is an integer of 1 or 2,LiSO₃C₂F₄SO₃Li, CF₃CO₂Li, C₄F₉SO₃Li, (CF₃CO)₂NLi, (CF₃SO₂)₃CLi,(CF₃SO₂)₂CFLi.
 3. A flexible mold according to claim 1, wherein saidlithium salt of an organic fluorine compound is blended in an amount of0.01 to 5% by weight relative to the amount of the resin materialforming said mold layer.
 4. A flexible mold according to claim 1,wherein said mold layer is transparent.
 5. A flexible mold according toclaim 1, wherein said mold layer consists of a hardened product of acurable resin material.
 6. A flexible mold according to claim 5, whereinsaid curable resin material is selected from the group comprising aphotocurable monomer, a photocurable oligomer, and mixtures thereof. 7.A flexible mold according to claim 6, wherein said curable resin isselected from the group comprising an acrylic monomer, an acrylicoligomer, and mixtures thereof.
 8. A flexible mold according to claim 7,wherein said curable resin is selected from the group comprising a(meth)acrylate monomer, a(meth)acrylate oligomer, and mixtures thereof.9. A flexible mold according to claim 8, wherein said (meth)acrylatemonomer and/or oligomer are/is selected from the group consisting ofurethane (meth)acrylate, polyester (meth)acrylate, polyether(meth)acrylate.
 10. A flexible mold according to claim 1, wherein saidmold layer has a thickness of 5 to 1000 μm.
 11. A flexible moldaccording to claim 1, wherein the mold further comprises a supportcarrying said mold layer.
 12. A flexible mold according to claim 1,wherein the mold is used for molding ribs of a back panel for a plasmadisplay panel.
 13. A flexible mold according to claim, wherein saidlithium salt of an organic fluorine compound is not decomposed thermallyat temperature below 200° C. during the course of molding process usingsaid mold.
 14. A flexible mold according to claim 1, wherein said groovepattern of the mold layer is a straight pattern composed of a pluralityof grooves arranged at a constant spacing generally in parallel to eachother.
 15. A flexible mold according to claim 1, wherein said groovepattern of the mold layer is a lattice-shaped pattern composed of aplurality of grooves arranged so as to cross at a constant spacinggenerally in parallel to each other.
 16. A flexible mold according toclaim 1, wherein, in said mold layer, said groove pattern is defined byplane portions and grooves, and wherein said groove has depth of 100 to400 μm and width of 50 to 250 μm as measured at the surface of said moldlayer.
 17. A flexible mold according to claim 11, wherein said supportis a film of plastic material.
 18. A flexible mold according to claim17, wherein said plastic material is at least one plastic materialselected from the group consisting of polyethylene terephthalate,polyethylene naphthalate, stretched polyethylene, polycarbonate, andtriacetate.
 19. A flexible mold according to claim 11, wherein saidsupport has a thickness of 50 to 500 μm.
 20. A method of manufacturing aflexible mold which has a mold layer provided on the surface thereofwith a groove pattern having specified shape and size, said methodcomprising the steps of: forming a layer of a photocurable resinmaterial by coating a photocurable resin material containing a lithiumsalt of an organic fluorine compound as an antistatic agent to apredetermined film thickness on a metal master pattern having on thesurface thereof a protrusion pattern in shape and size corresponding tosaid groove pattern of said mold; laminating a transparent supportconsisting of a film of plastic material on said metal master pattern tothereby form a laminate of said metal master pattern, said layer of aphotocurable resin material, and said support; irradiating said laminatewith light from the side of the support to harden said layer ofphotocurable resin material; and releasing said mold layer formed by thehardening of said photocurable resin material together with said supportfrom said metal master pattern.
 21. A method of manufacturing a finestructure having a protrusion pattern of specified shape and size on thesurface of a substrate, said method comprising the steps of: providing aflexible mold having a mold layer which has on the surface thereof agroove pattern of shape and size corresponding to said protrusionpattern, said mold layer containing a lithium salt of an organicfluorine compound as an antistatic agent; placing a curable moldingmaterial between said substrate and said mold layer of said mold, andfilling said molding material into said groove pattern of the mold;hardening said molding material and forming a fine structure consistingof said substrate and the protrusion pattern integrally connectedthereto in one unit; and removing said fine structure from the mold. 22.A method of manufacturing a fine structure according to claim 21,wherein said fine structure is a back panel for a plasma display panel.